Glycogenosis type IB: possible membrane transport defect.

We have described a 20-month-old child with type IB glycogen storage disease, based on clinical and biochemical manifestations. Functional testing data were similar to those found in glucose-6-phosphatase deficiency, but in vitro studies showed normal hepatic glucose-6-phosphatase activity. Disruption of membranes with deoxycholic acid was followed by an increase in enzyme activity compared to a control liver tissue, suggesting "latency" of enzyme. We suggest that this patient had glycogen storage type IB and that this disorder may represent a specific glucose-6-phosphate transport defect.